Consumers are putting their homes at risk by trusting unqualified solar power installers and substandard equipment, industry experts say.

Solar power equipment has become much cheaper over the past six months and that has prompted DIYers and unqualified people to import, sell and even advise on the installation of the systems.

Solar power specialist electrician Phil Rumble said he had been called to two jobs in recent months where people had paid for systems that did not work as they were meant to.

For high-voltage work, such as house wiring, certified electricians need to provide final sign-off. "But people are selling gear, designing gear and telling [customers] they can put it in themselves."

He said there was a lack of oversight in the solar power industry.

Adrian Kerr, of the Solar Association of New Zealand, said the price drop had made a big difference.

Solar panels had dropped from about $4 a watt to 60c in six months. "It's now more accessible to import panels without much oversight."

He said even some qualified electricians were not familiar with solar technology because it was new.

An incorrectly installed system could void house insurance policies.

A representative of an Australasian solar power equipment supplier, who did not want to be identified, said it was a nationwide problem. He had written to a chain of importers and distributors, telling them batteries were repeatedly failing because of incorrect installation.

"System failure apparently is not covered under warranty, so the end user is suffering. Why this practice appears to continue, legally, is completely beyond me."

Waipu couple Maria Gabriel and Cedric Marshall spent $20,000 on a system that was installed by local firm Go Solar. Gabriel said the company's owner, Mid Beckett, designed the system and sold them the equipment, but did not help with installation. They had been told the system's batteries were not sufficient to support the size of the system and would soon fail.

Having the system fixed would cost thousands, plus replacing the eight batteries at $300 each.

But Beckett said they had only bought half the number of batteries recommended. Similar industry concerns were raised years ago about solar water systems. "Yes, we had some pretty rough installations. But the problem was really the imported equipment was failing. The two biggest players were the worst - and did not honour the guarantees. I know even some of the stuff I fitted turned out to be rubbish."

Panels save over $100

Mai Digby says crippling power bills are now a thing of the past after a solar panel system sent her bill plummeting to a paltry $14.99. Digby won the Right House solar panel competition in the Herald on Sunday last September.

It took a few weeks to get the system running. After the installation, Digby switched from Mercury to Meridian and last month produced and sold 420 kilowatt hours - almost as much as the household consumed.

Green Party energy spokesman Gareth Hughes said, "New Zealand needs a clear rule that the electricity company must purchase power off the person producing it at a fair rate."

Digby advised all Kiwis to think of alternatives. "You can save at least $100 a month."

Although the panels would probably produce less energy in winter, the system could generate 4160kw a year.